1. Field of the Invention
The present invention relates to a receiving apparatus and a receiving circuit which are used for, for example, digital broadcasting and the like.
2. Description of the Prior Art
The orthogonal frequency division multiplexing (OFDM) system has been used as a modulation system of digital broadcasting. The system is a modulation system of transmitting a plurality of electric waves such as an image, a sound and data broadcasting in the state of being multiplexed. Although the OFDM system has been used as a modulation system of the digital terrestrial television broadcasting, research has been made also to the use in mobile communications in recent years.
As a receiving apparatus which receives a signal of digital broadcasting adopting such an OFDM system, a diversity receiving apparatus equipped with a plurality of antennas connected to the diversity receiving apparatus to select a received signal or to synthesize (maximum specific synthesis) received signals according to the received electric field strength of the signal received by each antenna is known.
However, when noises have occurred in the same band as a receiving band in case of the diversity receiving apparatus described above, the received signals which have been received with the antenna and the noise signals are added, and the received electric field strength of the antenna becomes large. Then, a received signal including a noise signal having large received electric field strength is selected, or the received signal is included in the synthesis, and a received signal is thus obtained. As mentioned above, in comparison of the simple received electric field strength by a plurality of antennas, there has been a case where the reception characteristic becomes worse conversely.
Furthermore, as the problems common to the conventional diversity receiving apparatus, because the receiving circuits of the same number as that of the plurality of antennas are needed in addition to the antennas, there are the problems of the increasing cost of the receiving apparatus and the increasing power consumption thereof in addition to the problem of the increasing scale of the receiving apparatus. Then, because such a diversity receiving apparatus is needed to incorporate a plurality of antennas into the receiving apparatus, the miniaturization thereof is difficult and it is not suitable for being built in a cellular phone, a small television for automobile use, and the like.